1. Field of the Invention
The invention relates to medical sponges. More specifically, the invention is a medical sponge with reduced sticking properties and a method of making such a sponge.
2. Description of the Related Art
Medical sponges are widely used as bandages, diagnostic swabs, as surgical sponges for orthopedic, plastic, eye, ear, nose and throat procedures, as well as in other applications. For example, it is known to use medical sponges as surgical packing or dressings. During many surgical procedures, for example procedures in the anatomical cavity, sponges are used to absorb blood and to isolate the various organs from the operating field. The latter is accomplished by packing the organs with sponges to restrain them from interfering with the operation. In nasal and sinus procedures, sponges are used as packings to prevent excessive bleeding and swelling and often are left in place for several days or even weeks.
A condition known as "sticking" renders it difficult to remove packings constituted of conventional medical sponges because the sponges tend to adhere to tissue. Several primary factors cause adhesion. First, adhesion results from the healing process where tissue grows into the structure of the sponge used as packing material or a dressing. Healing adhesion is a particular problem when packing the mucosal linings of nasal or sinus passages. Second, difficulty in removing packings from nasal and sinus passages, or other small passages, arises from the relatively small cross sectional area of the passages and the resulting frictional resistance of the packing as it passes through the passage. Third, dried blood and other exudate in and around a wound tend to dry in place, thereby binding a sponge used as dressing to the wound.
A common surgical sponge is made of a cellulose material. Also, gauze pads and polyurethane materials are used for surgical sponges. More recently, a sponge material made from a reaction of polyvinyl alcohol (or polyvinyl acetal) and an aldehyde (such as formaldehyde) has been used. This sponge material, known as a PVA sponge material and sold by Merocel Scientific Products, is absorbant and low in particulate matter. The PVA sponge can be formed by reacting polyvinyl alcohol and an aqueous formaldehyde solution in the presence of an acid catalyst under carefully controlled conditions to produce a sponge material suitable for medical use and having controlled pore size uniformly distributed throughout its volume. The PVA sponge is expandable, biocompatible, absorbent, lint free, soft, and fast wicking.
Instantaneous wicking and high liquid holding capacity is attained by controlling the temperature and time conditions and processing procedure by which the formaldehyde and the polyvinyl alcohol are mixed and reacted. The formaldehyde and polyvinyl alcohol are heated and mixed in the presence of a surfactant to entrain an inert gas and to form pores of a uniform size. After a reaction, the sponge material is heated to cure the outer surface thereof and thus retain a stable overall shape. Thereafter, the sponge material is cured so that the sponge material experiences minimum shrinkage during the curing cycle. The cured sponge is then washed to remove unreacted chemical residue. The sponge material can be frozen and cut to shape for various applications. Pore size can be controlled through mixing or straining the mixture prior to curing. The PVA sponge and a method of making the PVA sponge is described in U.S. Pat. No. 4,098,728 issued to Rosenblatt, the disclosure of which is incorporated herein by reference. The PVA sponge, similar to other surgical sponges, is subject to sticking.
The use of coatings, films, and woven fibers of hyaluronic acid and its derivatives is also well known in various medical applications. Hyaluronic acid is a linear polymer present in the pericellular gels of connective tissues of vertebrates, articular synovial liquid, the vitreous humor, the tissue of the human umbilical cord, and cock's combs. For example, hyaluronic acid is known to lack inflammatory activity and is therefore useful to facilitate cicatrization, to replace endobulbar fluids, and for joint therapy. Also, it is known that hyaluronic acid promotes tissue repair. Esters of hyaluronic acid are known to be useful in cosmetic applications and for forming biodegradable plastics. U.S. Pat. No. 5,503,848 issued to Perbellinni et al discloses various applications for hyaluronic acid and esters thereof, as well as a "spongy" material made essentially of hyaluronic acid. However, previously, hyaluronic acid and its esters have not been combined with surgical sponges used as packings and dressings.
Overlays of silk, rubber, and the like, and coatings of materials such as polyethylene, lubricating gels and cremes have been used to alleviate patient discomfort upon withdrawal of packings. However, sticking of packing and dressings is still a problem.